java - Why answer is coming as 2:2:1:1 when we are removing all elements of a SET -

when add elements in set,it discard duplicate values.when removing elements of set k1 , k2. still final size 1. answer of code 2:2:1:1.

class keymaster {     public int i;      public keymaster(int i) {         this.i = i;     }      public boolean equals(object o) {         return == ((keymaster) o).i;     }      public int hashcode() {         return i;     } }   public class mapit  {      public static void main(string[] args) {         set<keymaster> set = new hashset<keymaster>();         keymaster k1 = new keymaster(1);         keymaster k2 = new keymaster(2);         set.add(k1);         set.add(k1);         set.add(k2);         set.add(k2);          system.out.print(set.size() + ":");         k2.i = 1;          system.out.print(set.size() + ":");         set.remove(k1);          system.out.print(set.size() + ":");         set.remove(k2);          system.out.print(set.size());     } } 

this because key in hashset not immutable when change field value of k2, field value changed object remain same, when want remove k2 set, cant find k2 because object have been changed.

for understanding better let k1 go , test this:

class mapit {     public static void main(string[] args) {         set<keymaster> set = new hashset<keymaster>();         keymaster k2 = new keymaster(2);         set.add(k2);         set.add(k2);          system.out.print(set.size() + ":");         k2.i = 3;         system.out.print(set.size() + ":");         set.remove(k2);          system.out.println(set.size());     } }